Christina Norman, lead gameplay designer on the Mass Effect series, and a name you may have heard associated with the drastic gameplay changes that occurred between the first and the second chapter of the trilogy, left BioWare as stated both by community manager Chris Priestly on the BioWare social network and by the former lead gameplay designer herself on her Twitter account. The reasons appear to be linked to her personal life and not tied to the game's production:

I removed Christina Norman from the Twitterinformation section as Christina has left BioWare (she recently got married and she and her husband moved away from Edmonton).

You are still welcome to follow Chistina if you want (she is a very interesting person and a lot of fun on Twitter), but she isn't part of the Mass Effect or BioWare teams anymore, so I removed her info.